Machine-to-machine (M2M) refers to all technologies and means for establishing connections between machines. The concept of M2M appeared in the nineties of 20th century, and only stayed in the theoretical stage then. After 2000, with the development of mobile communication technology, the mobile communication technology can be adopted to achieve networking of the machines. In 2002, the M2M service appeared in the market, and has been rapidly developed in the following years, and has become a focus of a large amount of telecommunications equipment manufacturers and telecom operators. Currently, in the worldwide, the number of machines is much more than the number of people, therefore, the M2M technology has good market prospects. Meanwhile, the M2M service has proposed many new requirements on the system, and in order to enhance the competitiveness of the mobile networks in this regard, it needs to optimize the existing mobile networks so as to more effectively support the M2M communication.
The existing mobile communications network is primarily designed for interpersonal communication, and is not optimized enough for the machine-to-machine communication and the man-to-machine communication. If an operator wants to provide the M2M communication service at low cost, it should reuse existing networks to the most extent, and reduce the impact of the M2M communication on networks as well as and the complexity of operation and maintenance.
In order to effectively use the existing mobile network resources, the 3rd Generation Partnership Project (3GPP) proposes services based on machine type communication (MTC), including M2M and machine-to-man communications, its service scope is far beyond the conventional human to human (H2H) communication. The MTC is very different from the existing H2H communication mode in terms of access control, billing, security, quality of service (QoS), and service mode.
The existing 3GPP system architecture comprises: radio access network and core network.
Herein the radio access network may be a Universal Terrestrial Radio Access Network (UTRAN), an Evolved UTRAN (E-UTRAN) or a GSM EDGE Radio Access Network (GERAN).
The core network comprises: Mobility Management Entity (MME), Serving Gateway (S-GW), PDN gateway (P-GW) and other network elements. The General Packet Radio Service (GPRS) core network comprises: Serving GPRS Support Node (SGSN) and other network elements.
The Non Access Stratum (NAS) refers to the control plane high stratum between the User Equipment (UE) and the MME/SGSN, and is located above the Access Stratum (AS). The NAS is mainly responsible for related functions and processes that are not related to the access technologies and are independent of the radio access.
When initiating an NAS connection request, the MTC UE comprises a low priority indication in the NAS request message, the MTC UE first establishes a radio bearer connection with the radio access network, then the UE sends an AS message carrying the NAS request message to the radio access network, and the radio access network forwards the NAS request message to the core network. Because in general the MTC UE is not sensitive to delay, it is considered to be a UE with a low priority. When a network congestion occurs, the network side can reject low-priority requests.
For example, when the radio access network is a UTRAN, the radio access network nodes of the UTRAN comprise Radio Network Controller (RNC) and Node B (NB), the UE sends the AS message carrying the NAS request message to the node B, and the node B forwards the AS message to the RNC, and then the RNC forwards the NAS request message to the SGSN over the Iu interface.
When the radio access network is the E-UTRAN, a radio access network node of the E-UTRAN comprises an evolved Node B (eNB). The UE sends an AS message carrying an NAS request message to the eNB, and the eNB carries the NAS request message in a signaling and sends it to the MME over the S1-MME interface.
In the abovementioned NAS connection establishment method, the radio access network carries the NAS request message in the signaling and sends it to the SGSN/MME, the SGSN/MME needs to read the signaling to obtain the NAS message, and then learns the priority of the NAS request message by reading the content of the NAS message. If a network congestion occurs, the SGSN/MME cannot quickly judge the priority of the NAS request and thus cannot quickly perform an effective control on the network congestion.